The present invention relates to a thrust reverser. More particularly, the invention relates to a cascade thrust reverser for braking a Jet aircraft by thrust reversal.
It is common practice in many commercial and military jet aircraft to brake the aircraft upon landing by effectively reversing the direction of thrust of the Jet engines. A common arrangement for providing such thrust reversal is to provide a pair of clam shell shaped blocker door members pivoted within the engine housing to swing from a position eclipsing openings in the engine housing to a position intercepting the thrust gases normally passing rearwardly of the engine thereby directing the gases out of the openings. Simultaneously with the swinging movement of the clam shell doors, partitions normally covering the housing openings swing outwardly and serve as a deflection or baffle wall for further guiding the outwardly deflected thrust gases forwardly thus providing the desired reverse thrust action.
The provision of the partition arrangements for cooperation with the clam shell structures in providing thrust reversal represents a substantial additional expense as well as an increase in weight of the overall aircraft. Furthermore, seals are required to prevent leakage between the blocker doors and the housing when such doors are in their stowed position. Moreover, there are many mechanical and hydraulic accessories necessary to operate such devices and as a consequence careful and periodic maintenance is required to assure reliability and safety.
A grid-like cascade vane structure has been fitted within the housing opening to replace the partition arrangement in known thrust reversers. The vanes in the grid structure are tilted forwardly slightly to provide the necessary forward component of gas flow necessary to realize a thrust reversal reaction. When the clam shell structures are in their normal inoperative position, they simply underlie the grid-like vane structure. Although this vane structure has advantages compared to the prior swinging partition type arrangements, it creates extra drag due to the positioning of the cascade vanes near the nacelle maximum cross-sectional area.
Thrust reversers are disclosed in U.S. Pat. Nos. 3,068,646; 3,931,944; 4,067,094; 4,129,269; 4,147,027 and 4,173,307.
Fletcher, in U.S. Pat. No. 3,068,646 discloses a thrust reverser arrangement which can be applied to a by-pass engine. The thrust reverser is connected to a by-pass air flow reverser. The by-pass passage is divided into two separate ducts along the sides of the engines and flaps interconnected with the engine thrust reverser are situated on the sides of the engine down-stream of the open ends of the by-pass duct portions and adapted when the engine thrust reverser is operative to move to position in which they cause the flow of by-pass air to be reversed.
Capewell et al, in U.S. Pat. No. 3,931,944, discloses a thrust reversal system for a jet aircraft engine, comprising thrust reverser buckets movable between a stowed and a deployed position. An air motor is operable under pilot's control to impart movement to the buckets. A piston is movable in a cylinder having restricted outlet orifices for automatically decelerating the motor when the buckets approach both the stowed and the deployed position. A locking mechanism locks the buckets in the stowed position and a flow control valve controls the direction of flow of operating air to the motor. The flow control valve, upon selection of deploy, initially occupies a position corresponding to movement of the motor in the direction to stow the buckets and, after release of the locking mechanism, moves to its alternative position to enable the motor to move the buckets to the deployed position.
Ittner, in U.S. Pat. Nos. 4,067,094 and 4,173,307, discloses a vane structure which fits within a side opening of an aircraft Jet engine normally covered by a pivoted clam shell arrangement. When the clam shell arrangement is actuated, it swings from the side opening in a direction to intercept thrust gases normally passing rearwardly of the engine and direct the gases laterally out of the side opening, the vane structure directing the gases upwardly and forwardly to provide a reverse thrust. The vane structure itself includes a number of beams lying in parallel vertical planes and a number of vanes in the form of continuous strips extending transversely to the direction of the beams, the beams having slots through which the vanes pass to define an egg crate like interlocked grid structure. The vanes are tilted forwardly slightly relative to the vertical to provide the forward component of gas movement creating the reverse thrust.
Fage, in the U.S. Pat. No. 4,129,269, discloses a thrust reverser for a Jet engine of an aircraft having two symmetrical doors mounted to pivot about an axis which is transverse and substantially diametrical with respect to the Jet of the engine and is disposed downstream of the jet exhaust pipe thereof The doors occupy a folded or stowed position in which they form part of the fairing of the engine or fuselage of the aircraft, or an unfolded or opened out position for which they are disposed transversely with respect to the jet.
Greathouse, one of the inventors of the present invention, in U.S. Pat. No. 4,147,027, discloses a thrust reverser nozzle for coaxial-flow turbofan engines comprising target-type deflector doors which are hinged for deployment about a fixed axis by means of actuation about single fixed pivots mounted on support structure on either side of the engine nacelle rearward portion. The deflector door's outer surfaces are shaped to match existing aerodynamic contours of the aircraft engine nacelle to provide a lower boattail angle for improved drag characteristics in the stowed or normal flight position. In that position, the deflector door interior configuration comprises a portion upstream of the engine exhaust nozzle exit plane and a downstream "fishmouth" portion through which flows hot engine exhaust gases surrounded circumferentially by cool air discharged from the engine fan. Geometry of the stowed fishmouth is sized and shaped to take advantage of mixing and shearing action between the exhaust streams so as to produce a desired variable area nozzle effect on the engine operation and thereby improve its forward thrust performance. Geometry of the upstream portion of the inside surface of the doors is sized and shaped with end plates so that when the deflector doors move to the deployed position, the exhaust streams are diverted outward and forward to produce a desired level of reverse thrust.
The principal object of the invention is to provide a cascade thrust reverser of simple structure which is efficient, effective and reliable in operation.
An object of the invention is to provide a cascade thrust reverser in a nozzle shaped to provide greater engine thrust at takeoff and less fuel consumption at cruise than known stowed thrust reverser nozzles.
Another object of the invention is to provide a cascade thrust reverser having enhanced simplicity of structure by utilizing a single hydraulic actuator and simple three bar mechanism.
Still another abject of the invention is to provide a thrust reverser which eliminates air leakage at the juncture of the thrust reverser with the jet exhaust nozzle in which it is installed, without the need for seals.
Yet another abject of the invention is to provide a thrust reverser which, in the absence of hydraulic pressure in the actuator, moves its blocker doors to stow position.
Another abject of the invention is to provide a cascade thrust reverser having blocker doors which are interchangeable and therefore may be substituted for each other.
Still another object of the invention is to provide a thrust reverser having actuator attachment fittings which permit interchanging from side to side.
Yet another object of the invention is to provide a thrust reverser having exhaust directing exposed vanes located at the aft end of the nacelle housing the nozzle to reduce drag considerably relative to a mid-nacelle location due to the shortened surface downstream of the vanes.